1. Field of the Invention The present invention relates to a method of treating an inkjet liquid (printing liquid) such as an ink or a processing liquid used in printing with an inkjet recording apparatus. Further, the invention relates to an inkjet recording apparatus, an inkjet liquid storage tank, and liquid absorber for inkjet liquid storage and an inkjet liquid treatment apparatus using the method.
2. Description of the Related Art
In inkjet recording methods, a liquid or melt solid ink is fired from nozzles, slits, porous films and the like, to perform recording on paper, cloth, film and the like. These methods have features of small size, low cost and silence and are used in a lot of printers. Among them, a piezo inkjet method of firing a liquid ink from a nozzle utilizing deformation of a piezoelectric element and a heat inkjet method which utilizes a heat boiling phenomenon are excellent in resolution and printing speed. Therefore, these methods are frequently utilized.
Inkjet recording is a promising recording technology as described above, however, it has a problem of poor discharge of ink. There are various causes for poor discharge, and drying and thickening of an ink in a nozzle, and clogging of a nozzle with bubble, refuse and the like can be exemplified. As technologies developed for solving such problems, a technology of covering a nozzle with a cap during non-printing period, a technology of providing a suction apparatus for discharging thickened inks, bubbles and refuses, a technology of empty firing, so-called dummy jet, and the like, can be exemplified. Among suggested technologies are technologies of providing an ink suction mechanism (see, Japanese Patent Application Laid-Open (JP-A) Nos. 56-60256, 57-12655, 62-113556 and 63-295265) and a technology of wiping off an ink adhered on the end surface of a head body by a wiper member (JP-A No. 62-251146). Owing to development of such technologies, improvement in poor discharge has been tried.
On the other hand, it has been recently desired to print at high speed and with high image quality particularly on regular paper. Therefore, various methods have been suggested to improve image density and to improve bleed of a single color and inter-color bleed. In a method suggested in JP-A No. 6-106735, in an ink set, color inks contains a surfactant that promotes permeation, and a solvent and salt, and the black ink contains a component causing thickening or coagulation under an influence of a salt. In a method suggested in JP-A No. 10-272768, pH of a color ink is 5 or lower, coagulation of a black ink is caused by contact of a black ink having weak ion strength with a color ink having strong ion strength, to improve water resistance and inter-color bleed. Examples of the compound enhancing the ion strength of a color ink in this method include monovalent and polyvalent chlorides, fluorides, bromides, nitrates and tosylates of alkali metals and alkaline earth metals.
However, when components thus causing coagulation are used in inks and processing liquids, in the maintenance part including a disposal apparatus that disposes of an ink and processing liquid, it is necessary to dispose of inks and processing liquids separately if the inks and the processing liquids cause coagulation and thickening when mixed. Consequently, an inkjet recording apparatus becomes larger and the cost increases.
There is a maintenance part that fires inks and processing liquids from each nozzle immediately before formation of an image (dummy jet) and prevent the discharge at the formation of an image from becoming faulty. There is also a method in which a cap is provided on each head to prevent drying of inks and processing liquids in a nozzle part, and the inks and the processing liquids are sucked by a pump while the nozzles are capped, to remove from a nozzle inks and processing liquids that were thickened when they dried. In these example, usually, a waste liquid composed of inks and processing liquids generated during maintenance is recovered through a tube to a waste ink tank that stores a waste liquid. In many cases, in the waste ink tank, a porous body such as urethane foam or a fibrous material such as polyester felt is used as an absorber, and this absorber absorbs the waste liquid composed of inks and processing liquids.
If the inks and the processing liquid which coagulate or thicken when mixed are mixed and disposed of in a part of disposal device in such a maintenance section, a problem occurs. For example, clogging with a coagulated substance occurs in a pump that sucks inks and processing liquids. Clogging with a coagulated substance occurs at the inlet or inside of a tube which is a route to a waste ink tank. Coagulation occurs in the upper or other specific part of an absorber provided in a waste ink tank to disturb absorption of inks and processing liquids. In that case, the absorber and the waste ink tank can store less waste liquid than expected. Because of these problem, the respective parts cannot function well and the apparatus becomes faulty.
In order to avoid these problems, when there are two or more combinations of printing liquids (ink-ink, ink-processing liquid) that can coagulate or cause coagulated substance when mixed, it is necessary to provide waste liquid processing parts separately for each combination of the printing liquids in a maintenance part. However, as a result, the number of parts of a waste liquid processing parts increases to elevate the cost and the machine size also increases. There is therefore a need for improved techniques for the treatment and disposal of liquids used in inkjet recording.